Handover method and apparatus in a wireless telecommunications network

Abstract

In handover in a wireless telecommunications network, dummy packets, or data packets with a last used sequence number indicator are transmitted from a source node eNB 2 to a target node 3 . When the target node eNB 3 detects the information, it knows the sequence of data packets being received from the source node eNB 2 and which is the last one and its sequence number. Thus, data packets may be suitable ordered for delivery to a mobile terminal UE 1.

1 . A method for handover of a mobile terminal from a source node to a target node in a wireless telecommunications network, including the steps of:
 during a handover procedure, the source node forwarding any data packets to the target node which sends them to the mobile terminal;   the source node adding a last used sequence number indicator to at least one packet to indicate the sequence number of the last data packet to be delivered by the source node to the target node; and   forwarding the packet with the indicator to the target node.   
   
   
       2 . The method as claimed in  claim 1  wherein the source node adds a last used sequence number indicator to a plurality of packets. 
   
   
       3 . The method as claimed in  claim 1  wherein the last used sequence number indicator is added to a data packet or data packets. 
   
   
       4 . The method as claimed in  claim 3  wherein the indicator is added to data packets buffered at the source node before forwarding to the target node. 
   
   
       5 . The method as claimed in  claim 3  wherein the indicator is added to data packets sent from to the source node to the target node without buffering at the source node. 
   
   
       6 . The method as claimed in  claim 1  wherein the last used sequence number indicator is added to a dummy packet or dummy packets. 
   
   
       7 . The method as claimed in  claim 1  wherein the telecommunications network is in accordance with Long Term Evolution (LTE) specifications. 
   
   
       8 . A wireless telecommunications network comprising a plurality of nodes and in which, during a handover procedure of a mobile terminal from a source node to a target node, the source node is arranged to forward data packets to the target node and add a last used sequence number indicator to at least one packet to indicate the sequence number of the last data packet to be forwarded by the source node to the target node, and the target node is arranged to send the forwarded data packets to the mobile terminal. 
   
   
       9 . A network node comprising a generator for adding a last used sequence number indicator to at least one packet to indicate the sequence number of the last data packet to be delivered by the node to another target node during handover. 
   
   
       10 . A network node as claimed in  claim 9  and including a generator for generating a dummy packet having a last used sequence number indicator.